Youtube fullscreen not working

When I hit the fullscreen button inside a youtube video in firefox, the
video just disappears, and I'm left with the browser without the video.
There's no new full-screen workspace created. Pressing either alt-tab or
Escape has the same effect: the video comes back into its original
position embedded inside the browser. I don't think I've ever had this
work correctly in the past either.

Any idea why this is happening/how to fix this?

Using ion3-2009-0110. The issue is probably similar/same as the issue in
[1].


[1] http://thread.gmane.org/gmane.comp.window-managers.ion.general/8699/focus=8699